1. Field of the Invention
This invention relates to collets for use in tube couplings for locking the tube in a coupling body and to methods of manufacturing such collets.
2. Background Prior Art
Our UK Patent Specification Nos. 1520742 and 1573757 describe and illustrate a number of forms of collets for locking tubes in coupling bodies. The collets disclosed comprise an annular collar having resilient arms formed with heads at the distal ends of the arms.
The coupling body with which the collet is used has an open ended throughway and the collet is located in the open end of the throughway with the arms extending from the collar into the throughway. The throughway is formed with a tapered cam surface narrowing towards the open end of the throughway with which the arms of the collet engage to be pressed inwardly with movement of the collet outwardly of the throughway. A tube is inserted through the collet into the throughway and the heads of the collet are forced into gripping engagement with the tube by the tapered cam surface to lock the collet in the coupling body.
Other arrangements of collet for locking a tube in a coupling body are described in our European Patent Specification Nos. 0691503, 0663557 and 0756125. In these arrangements a coupling body has an open ended throughway and a collet comprising a collar and resilient arms is located in the throughway with the arms extending towards the open end of the throughway. A tube to be locked in the coupling body has an encircling rib adjacent the end which the heads of the collet arms snap over when the tube is inserted into the coupling body. The heads of the arms engage in slots or abutments formed around the coupling body to prevent the collet from being drawn outwardly of the coupling body and hence the tube is restrained in the coupling body.
The collet is formed from plastics material which has the necessary flexibility to allow the arms to flex as required to grip and release the tube. The flexibility of the collet does impose some restriction on the overall load which the collet can withstand particularly at higher temperatures. An object of the present invention is to provide a collet which can withstand higher loads and particularly at higher temperatures than hitherto available.